Tungsten Alloy Class 2 Tungsten
ASTM B760 Class 2
Class 2 Tungsten is potassium-silicate (AKS) doped tungsten to ASTM B760 Class 2, in which the dopant produces an interlocking recrystallized grain structure that resists creep and sag at high operating temperature.
Reference datasheet — Class 2 Tungsten is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the SR condition
Class 2 Tungsten tempers and conditions
Class 2 Tungsten is supplied in 6 conditions, soft to hard. SR is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Sintered | Semi-finished doped tungsten billet as it leaves the sintering furnace; used only as feedstock for swaging, rolling or drawing. | 180 | 0 | 28 HRC | 25 % IACS | |
Recrystallized | Condition after >2200 °C exposure or deliberate anneal — the AKS bubbles produce long interlocking grains giving the best creep/sag resistance, at the cost of near-zero RT ductility. | 450 | 600 | 0.5 | 37 HRC | 172 W/m·K |
Rolled sheet/plate/foil, stress relieved | Cross-rolled doped tungsten sheet, plate and foil supplied stress relieved for furnace shielding, boats and high-temperature structural parts. | 700 | 850 | 4 | 40 HRC | 30 % IACS |
SRDefault Stress relieved | Default stocked condition for doped tungsten rod and wire: fibrous worked structure with residual stress removed, best balance of strength and handleability before service recrystallization. | 800 | 1,050 | 3 | 42 HRC | 163 W/m·K |
As-swaged / as-drawn | Maximum-strength worked condition; choose where the highest room-temperature tensile strength of rod or coarse wire is needed and residual stress is acceptable. | 1,450 | 1,700 | 2 | 50 HRC | 29 % IACS |
Fine drawn wire | Heavily drawn AKS filament wire; pick for lamp/heater coils and cutting wire where ultra-high as-drawn tensile strength is required. | 2,600 | 3,000 | 2 | 55 HRC | 31 % IACS |
What is Class 2 Tungsten?
Class 2 Tungsten is potassium-silicate (AKS) doped tungsten to ASTM B760 Class 2, in which the dopant produces an interlocking recrystallized grain structure that resists creep and sag at high operating temperature. It is chosen for filament, coil and hot-zone work, with 800 MPa yield, 1050 MPa tensile, about 3% elongation, 42 HRC, 163 W/m·K and a maximum service temperature of 2500 °C in vacuum or inert gas. Stock forms include sintered blanks, drawn wire, sheet and stress-relieved or recrystallized rod. Limits are brittleness below the ductile-brittle transition, a machinability rating of 10, weldability of 12 and rapid oxidation in air; use W-Re Class 4 when weld or bend ductility is required. Class 2 Tungsten has a density of 19.25 g/cm³ (0.695 lb/in³), heavier than 76% of tungsten alloy grades. It melts at 3,422°C (6,192 °F). Class 2 Tungsten has a yield strength of 800 MPa (116 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 56% of tungsten alloy grades. Elongation at break is 3% and the elastic modulus is 405 GPa (58.7 Msi).
What is Class 2 Tungsten used for?
- incandescent lamp filaments
- halogen lamp coils
- high-temperature heating elements
- vacuum furnace hardware
Advantages
- High service temperature — 2,500°C (4,532 °F), better than 95% of tungsten alloy grades
Limitations
- Low fracture toughness — 10 MPa·√m (9.1 ksi·√in), worse than 83% of tungsten alloy grades
- Hard to polish — 60/100, worse than 83% of tungsten alloy grades
Class 2 Tungsten properties
Typical room-temperature values for Class 2 Tungsten-SR; bars are the position among tungsten alloy grades.
Physical3
Class 2 Tungsten has a density of 19.25 g/cm³ (0.695 lb/in³), heavier than 76% of tungsten alloy grades. It melts at 3,422°C (6,192 °F).
Mechanical14
Class 2 Tungsten has a yield strength of 800 MPa (116 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 56% of tungsten alloy grades. Elongation at break is 3% and the elastic modulus is 405 GPa (58.7 Msi).
Thermal5
Class 2 Tungsten is rated for continuous service to 2,500°C (4,532 °F). It conducts heat at 163 W/m·K (94.2 BTU/hr·ft·°F), better than 62% of tungsten alloy grades. Thermal expansion is 4.5 µm/m·K (2.5 µin/in·°F).
Electrical3
Class 2 Tungsten conducts electricity at 30 % IACS, better than 64% of tungsten alloy grades.
Chemical & Environmental3
Corrosion resistance is good (68/100), better than 79% of tungsten alloy grades.
Sustainability4
Producing a kilogram of Class 2 Tungsten takes about 400 MJ of energy and emits 27 kg of CO₂ — more than 74% of tungsten alloy grades. Typical recycled content is 30%.
Manufacturability8
Class 2 Tungsten's machinability is not recommended (10/100, better than 52% of tungsten alloy grades); weldability not recommended (12/100); formability not recommended (8/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the tungsten alloy family
Yield strength against density for every tungsten alloy grade FabDigit runs. Class 2 Tungsten is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Class 2 Tungsten
Is Class 2 Tungsten easy to machine?
Treat as a grinding/EDM material — diamond or CBN grinding, wire EDM and laser cutting dominate; if turning, use rigid setups, negative-rake carbide at low speed and preheat to 200–400 °C to avoid chipping.
Can Class 2 Tungsten be welded?
Only electron-beam or laser welding in high vacuum gives usable joints, and the fusion zone recrystallizes to brittle coarse grains; vacuum brazing with Ni, Cu-Ag or Zr-based fillers is the preferred joining route.
Can Class 2 Tungsten be formed, bent or molded?
Cold forming is not feasible; bend, coil and draw warm (400–1200 °C depending on section) above the ductile-brittle transition, and avoid any post-recrystallization deformation.
Class 2 Tungsten chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Kresidual potassium from AKS doping (55–95 ppm) — the sag-resisting bubble former | 0.01 | 0.01 |
| Siresidual from silicate dopant | 0 – 0.01 | 0 |
| Alresidual from aluminate dopant | 5×10⁻⁴ – 0 | 0 |
| Fe | ≤ 0 | 0 |
| Mo | ≤ 0.01 | 0 |
| C | ≤ 0 | 0 |
| O | ≤ 0.01 | 0 |
| N | ≤ 0 | 5×10⁻⁴ |
| Ni | ≤ 0 | 0 |
| W99.95 % min excluding dopant residues | balance |
What surface finishes work on Class 2 Tungsten?
Chemically etch (alkaline ferricyanide or HF/HNO₃) or electropolish to remove drawing lubricant and surface defects; no anodizing — apply CVD/PVD or silicide coatings if oxidation protection above 500 °C is needed.
Equivalent designations
Standards and trade names that resolve to Tungsten Alloy Class 2 Tungsten in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- B760 Class 2
How much does Class 2 Tungsten cost?
Class 2 Tungsten is a high-cost tungsten alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Class 2 Tungsten — frequently asked
What is Class 2 Tungsten used for?
Class 2 Tungsten is typically used for incandescent lamp filaments, halogen lamp coils, high-temperature heating elements and vacuum furnace hardware. In short: sag-resistant doped tungsten; 2500 °C service in vacuum; standard lamp filament grade.
What is the yield strength of Class 2 Tungsten?
Class 2 Tungsten has a typical yield strength of 800 MPa (116 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 56% of tungsten alloy grades. Strength varies by condition: see the 6 listed tempers.
Is Class 2 Tungsten easy to machine?
Not especially — machinability is rated not recommended (10/100, better than 52% of tungsten alloy grades). Treat as a grinding/EDM material — diamond or CBN grinding, wire EDM and laser cutting dominate; if turning, use rigid setups, negative-rake carbide at low speed and preheat to 200–400 °C to avoid chipping.
Can Class 2 Tungsten be welded?
Not readily — weldability is rated not recommended (12/100). Only electron-beam or laser welding in high vacuum gives usable joints, and the fusion zone recrystallizes to brittle coarse grains; vacuum brazing with Ni, Cu-Ag or Zr-based fillers is the preferred joining route.
What surface finishes work on Class 2 Tungsten?
Chemically etch (alkaline ferricyanide or HF/HNO₃) or electropolish to remove drawing lubricant and surface defects; no anodizing — apply CVD/PVD or silicide coatings if oxidation protection above 500 °C is needed.
Can Class 2 Tungsten be formed, bent or molded?
Cold forming is not feasible; bend, coil and draw warm (400–1200 °C depending on section) above the ductile-brittle transition, and avoid any post-recrystallization deformation.
What is the maximum service temperature of Class 2 Tungsten?
Class 2 Tungsten is rated for continuous use to about 2,500°C (4,532 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Class 2 Tungsten-SR and Class 2 Tungsten-FW?
SR is the default condition — default stocked condition for doped tungsten rod and wire: fibrous worked structure with residual stress removed, best balance of strength and handleability before service recrystallization. FW: heavily drawn AKS filament wire; pick for lamp/heater coils and cutting wire where ultra-high as-drawn tensile strength is required. Yield strength is 800 MPa in SR versus 2,600 MPa in FW.
How much does Class 2 Tungsten cost?
Class 2 Tungsten is a high-cost tungsten alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B760 — Tungsten Plate, Sheet, and Foil — ASTM International (2017)
- ASTM F288 — Tungsten Wire for Electron Devices and Lamps — ASTM International (2018)
- GB/T 3875 / GB/T 4181 (2017)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (Refractory Metals) — ASM International (1990)
- Tungsten — material properties and product forms — Plansee SE (2023)
- Thermophysical properties of tungsten — CRC Handbook of Chemistry and Physics (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.